1. Department of Electronic and Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, United Kingdom
2. Hitachi Cambridge Laboratory, Hitachi Europe Ltd., Cambridge CB3 0HE, United Kingdom
3. Department
of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom
4. Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, United States
5. Gasp Solar ApS, Gregersensvej 7, Taastrup DK-2630, Denmark
6. Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, People’s Republic of China